Terpolyamides with hexamethylene terephthalamide,hexamethylene isophthalamide and caproamide units

ABSTRACT

FIBER-FORMING TERPOLYAMIDES CONSISTING OF HEXAMETHYLENE TEREPHTHALAMIDE UNITS, HEXAMETHYLENE ISOPHTHALAMIDE UNITS AND CAPROAMIDE UNITS. THE PROPETIES OF FIBERS FORMED FROM THESE TERPOLYMERS MAY BE CONTROLLED BY VARYING THE MOLE PROPORTION OF THE COMPONENTS FROM WHICH WHEY ARE PEPARED. THE TERPOLYMERS ARE PARTICULARYL USEFUL IN FORMING TEXTILE FIBERS AND TRANSPARENT FILMS AND CASTINGS.

United States Patent US. Cl. 260-78 A 3 Claims ABSTRACT OF THE DISCLOSURE Fiber-forming terpolyamides consisting of hexamethylene terephthalamide units, hexamethylene isophthalamide units and caproamide units. The properties of fibers formed from these terpolymers may be controlled by varying the mole proportion of the components from which they are prepared. The terpolymers are particularly useful in forming textile fibers and transparent films and castings.

This application is a continuation-in-part of applicants copending application S.N. 535,338, filed Mar. 18, 1966, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to synthetic fibers. More particularly, this invention relates to novel synthetic fibers composed of random terpolyamides.

Polyamides, such as polyhexamethylene adipamide (nylon 66) and polycaproamide (nylon 6) are well known in the art and have found significant commercial success both as textile fibers and as reinforcing fibers, such as tire cord. Although the textile fibers obtained from the previously known fiber-forming polyamides heretofore known are of great value, much research elfort is being continuously expended in order to improve their properties. For example, these previously known polyamides all possess a relatively low shrinkage value, that is, the amount of shrinkage that occurs in fibers made from these polyamides when they are treated with boiling water is relatively small. In some commercial uses, for example, as hosiery, it is desirable that the polyamide textile fiber have increased shrinkage. Furthermore, in the production of conjugate fibers, that is, a fiber having two or more components, it is extremely desirable that at least one of the components have a relatively high boiling water shrinkage. This is necessary in order that the crimp in a conjugate fiber be significant and permanent.

While, as pointed out heretofore, previously known polyamides have significant use in the reinforcement of rubber articles such as vehicle tires, an inherent drawback in their use to reinforce such tires is their tendency to flatspot. Flatspotting is a term used to describe the out-ofroundness that occurs when a polyamide-reinforced vehicle tire is allowed to rest for a period of time. That portion of the tire which is in contact with the pavement becomes flattened and when the vehicle is started again this flatspot causes vibration of the vehicle. While this phenomenon of fiatspotting is not completely understood, there is at present a great deal of effort being put into finding a solution to this problem as regards polyamide tire cords.

It is an object of this invention to provide a novel synthetic fiber composed of a random terpolyamide, the properties of which can be controlled by varying the mole proportion of its components.

3,787,373 Patented Jan. 22, 1974 It is a further object of this invention to provide a novel synthetic fiber composed of a terpolyamid which has increased boiling water shrinkage characteristics.

It is a further object of this invention to provide a synthetic fiber of hexamethylenediamine terephthalic acid, hexamethylene isophthalic acid, and e-caprolactam or 6- aminocaproic acid.

These and other objects will become apparent from the description given hereinafter.

In accordance with the present invention it has been found that these objects are accomplished by providing a novel synthetic fiber comprising a random terpolyamide consisting essentially of (A) 5-60 percent, based on the molecular weight of the terpolyamide, of hexamethylene terephthalamide units, (B) 5-60 percent, based on the molecular weight of the terpolyamide, of hexamethylene isophthalamide units, and (C) 10-90 percent, based on the molecular weight of the terpolyamide, of caproamide units. In a preferred form of this invention, the synthetic fiber is composed of 10-40 percent hexamethylene terephthalamide units, 10-40 percent hexamethylene isophthalamide units, and 20-80 percent of caproamide units.

In the following description of the invention, polymer compositions are reported in terms of mole percent 6T, or hexamethylene terephthalamide component, mole percent 61, or hexamethylene isophthalamid component, and mole percent 6 which refers to caproamide component. This is a convenient means of describing the polymers since, in practice, they are prepared by copolymerizing a mixture of hexamethylenediammonium terephthalate salts, hexamethylenediammoniurn isophthalate salts, and 6-aminocaproic acid or caprolactam. The final polymer product of the invention is a statistically random nylon copolymer comprised of the polymerization product of hexamethylene diamine, isophthalic acid, terephthalic acid and 6- aminocaproic acid or caprolactom.

The terpolymers are conveniently prepared by polymerization of aqueous solutions of the components in the manner well known in the preparation of nylon 66.

The terpolymers may be produced in any conventional manner, for example, in batch procedures where the polymer is prepared, extruded, cut into flakes and thereafter spun. They may also be prepared by continuous processes in which the reactants are fed to a system comprising an evaporator, polymerizer, finisher and spinning unit in tandem so that molten polymer is spun directly without intermediate solidification.

As with conventional nylon production, various additives may be introduced into the polymer for purposes of delustering, stabilization toward heat and the like. Additives for these and other like purposes are well known in the art.

The solution from which the random terpolyamides are made may be prepared by combining solutions of hexamethylenediammonium isophthalate, hexamethylenediammoniurn terephthalate and 6-aminocaproic acid, or by adding a calculated excess of hexamethylene diamine together with the calculated quantities of terephthalic acid and isophthalic acid directl to the 6-aminocaproic acid or e-caprolactom solution. In the following examples compositions are given in mole percent unless otherwise indicated.

EXAMPLE This example is illustrative of a typical method for preparing the terpolymers.

A mixture consisting of 30 mole percent hexamethylene diammonium terephthalate, 10 mole percent hexamethylene diammonium isophthalate and 60 mole percent 6- aminocaproic acid were added to sufficient water to provide a 50 percent aqueous slurry. The slurry was charged to an evaporator and after purging the evaporator with 250 poundse per square inch saturated steam to remove air, the evaporator was closed at a residual steam pressure of 13 p.s.i. Evaporative heating was carried out with part of the water being removed while maintaining 13 pounds pressure. The solution was then transferred to an autoclave, heated to approximately 260 C. and the pressure brought to 250 pounds per square inch. The solution was then heated for three hours, and water was bled off to maintain a steady 250 psi. pressure. The pressure was then gradually reduced to atmospheric during which time the temperature rose to approximately 290 C. and the heating was continued for an additional hour. Monofilaments were spun from the bottom of the autoclave onto a Universal take-up and drawn over a 50 C .-90 C. hot pin to a denier of approximately 10.

Six additional yarns were prepared according to the foregoing procedure in which the mole ratio of the polymer components was varied as indicated in the table. Properties of the six yarns were determined and are given in the table. The percent boiling Water shrinkage was determined by immersing a length (11 inches) of fiber into boiling water for 15 minutes; removing and drying the fiber; and determining its shrinkage. The percent shrinkage represents the change in the length of the fiber sample expressed as a percentage of the length prior to exposure to boiling water. Initial modulus was determined according to ASTM-02256-66T procedure.

The data in the table show that the terpolymer yarns have improved initial modulus; fabrics prepared from high initial modulus yarns resist wrinkling. The terpolyrner yarns also have relatively high boiling water shrinkage which is desirable in hosiery yarn and in the production of conjugate fibers. Moreover, since the terpolymers are transparent they are suitable for manufacturing castings, films and the like.

We claim:

1. A synthetic terpolyamide fiber, composed of random terpolyamide consisting essentially of (A) 5-60 percent, based on the weight of the terpolyamide, of hexamethylene terephthalamide units, (B) 5-60 percent, based on the weight of the terpolyamide, of hexarnethylene isophthalamide units, and (C) 10-90 percent, based on the weight of the terpolyamide, of caproamide units.

2. A fiber as defined in claim 1 wherein the terpolyamide consists essentially of (A) 10-40 percent of hexamethylene terephthalamide units, (B) 10-40 percent of hexamethylene isophthalamide units, and (C) 20-80 percent of caproarnide units.

3. A ternary fiber-forming copolyamide consisting essentially of (1) 5-60 percent by weight of hexamethylene terephthalamide units, (2) 5-60 percent by weight of hexamethylene isophthalamide units and (3) 10-90 percent by weight of caproamide units.

References Cited UNITED STATES PATENTS HAROLD D. ANDERSON, Primary Examiner US. Cl. X.R.

57-l40 R; 167-227; 260-48 L 

